手写简易线程池

/**手写简易的线程池
 * @author 胡庆安
 * @version V1.0
 * @Package Thread.pool
 * @date 2020/10/23 10:57
 * @Copyright © 2010-2020 爬山虎科技（扬州）股份有限公司
 */
public class HqaPool {

    /**
     * 核心线程数
     */
    int coreSize;
    /**
     * 队列存放最大任务数
     */
    int capcity;
    /**
     * 闲置多久线程会被会被回收
     */
    long times;

    HashSet<Task> tasks = new HashSet<>();

    BlockingQueue queue;

    public HqaPool(int coreSize, int capcity, long times) {
        this.coreSize = coreSize;
        this.capcity = capcity;
        this.times = times;
        queue = new BlockingQueue(capcity);
    }

    //执行任务
    public void execute(Runnable task){
        synchronized (tasks){
            Task taskRe = new Task(task);
            //如果任务没有超过coreSize,直接交给Task对象执行
            if(tasks.size()<coreSize){
                tasks.add(taskRe);
                taskRe.start();
            }else {//如果任务超过了coreSize,直接添加到队列等待
                queue.put(taskRe);
                System.out.println("任务"+taskRe+"被添加到了队列里");
            }
        }
    }

    /**
     * 阻塞任务队列（存放任务）
     */
    class BlockingQueue{

        private Deque<Task> deque = new ArrayDeque<Task>();
        public ReentrantLock lock = new ReentrantLock();
        private int capcity;
        //生产者条件变量
        private Condition fullWaitSet = lock.newCondition();
        //消费者条件变量
        private Condition emptyWaitSet = lock.newCondition();

        public BlockingQueue(int capcity) {
            this.capcity = capcity;

        }

        //任务放入阻塞队列
        public void put(Task task){
            lock.lock();
            try {
                while (deque.size() == capcity){
                    try {
                        fullWaitSet.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                deque.add(task);
                emptyWaitSet.signal();
            }finally {
                lock.unlock();
            }

        }

        //任务取出阻塞队列
        public Task take(){
            Task task;
            lock.lock();
            try {
                while (deque.size() == 0){
                    try {
                        emptyWaitSet.await();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                task= deque.removeFirst();
                fullWaitSet.signal();
            }finally {
                lock.unlock();
            }

            return task;
        }

        //获取阻塞队列当前的size
        public int size(){
            lock.lock();
            try {
                return deque.size();
            }finally {
                lock.lock();
            }

        }

    }

    /**
     * 线程池任务
     */
    class Task extends Thread{
        private Runnable task;

        public Task(Runnable task) {
            this.task = task;
        }

        @Override
        public void run() {
            while (task!=null||(task=queue.take()) != null){//请细品
                try {
                    System.out.println("任务"+task+"被执行了");
                    task.run();
                }catch (Exception e){
                    e.printStackTrace();
                }finally {
                    task = null;
                }
            }
        }
    }
}

测试main方法：

public static void main(String[] args) {
        HqaPool pool = new HqaPool(2, 10, 1000);
        for (int i = 0; i < 15; i++) {
            pool.execute(() -> {
                try {
                    Thread.sleep(5000L);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            });
        }
    }

注意上面的程序当线程逻辑执行完之后程序不会结束，会一直阻塞在task=queue.take()那里，所以我们手写线程池2.0 的版本会给阻塞队列添加超时获取的功能以及拒绝策略等功能。。。。。。。

 

下面是2.0 版本：

/**
 * @author 胡庆安
 * @version V2.0
 * @Package Thread.pool
 * @date 2020/10/23 14:01
 * @Copyright © 2010-2020 爬山虎科技（扬州）股份有限公司
 */
public class ThreadPool {
    Logger log = LoggerFactory.getLogger(ThreadPool.class);
    // 任务队列
    private BlockingQueue<Runnable> taskQueue;
    // 线程集合
    private HashSet<Worker> workers = new HashSet<>();
    // 核心线程数
    private int coreSize;
    // 获取任务时的超时时间
    private long timeout;
    private TimeUnit timeUnit;

    // 执行任务
    public void execute(Runnable task) {
        // 当任务数没有超过 coreSize 时，直接交给 worker 对象执行
        // 如果任务数超过 coreSize 时，加入任务队列暂存
        synchronized (workers) {
            if (workers.size() < coreSize) {
                Worker worker = new Worker(task);
                log.debug("新增 worker{}, {}", worker, task);
                workers.add(worker);
                worker.start();
            } else {
                // taskQueue.put(task);
                // 1) 死等
                // 2) 带超时等待
                // 3) 让调用者放弃任务执行
                // 4) 让调用者抛出异常
                // 5) 让调用者自己执行任务
                taskQueue.offer(task,1000,TimeUnit.SECONDS);
            }
        }
    }

    public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapcity) {
        this.coreSize = coreSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.taskQueue = new BlockingQueue<>(queueCapcity);
    }

    class Worker extends Thread {
        private Runnable task;

        public Worker(Runnable task) {
            this.task = task;
        }

        @Override
        public void run() {
            // 执行任务
            // 1) 当 task 不为空，执行任务
            // 2) 当 task 执行完毕，再接着从任务队列获取任务并执行
            // while(task != null || (task = taskQueue.take()) != null) {
            while (task != null || (task = taskQueue.poll(timeout, timeUnit)) != null) {
                try {
                    log.debug("正在执行...{}", task);
                    task.run();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    task = null;
                }
            }
            synchronized (workers) {
                log.debug("worker 被移除{}", this);
                workers.remove(this);
            }
        }
    }

    class BlockingQueue<T> {
        // 1. 任务队列
        private Deque<T> queue = new ArrayDeque<>();
        // 2. 锁
        private ReentrantLock lock = new ReentrantLock();
        // 3. 生产者条件变量
        private Condition fullWaitSet = lock.newCondition();
        // 4. 消费者条件变量
        private Condition emptyWaitSet = lock.newCondition();
        // 5. 容量
        private int capcity;

        public BlockingQueue(int capcity) {
            this.capcity = capcity;
        }
// 带超时阻塞获取
public T poll(long timeout, TimeUnit unit) {
lock.lock();
try {
// 将 timeout 统一转换为 纳秒
long nanos = unit.toNanos(timeout);
while (queue.isEmpty()) {
try {
// 返回值是剩余时间
if (nanos <= 0) {
return null;
                        }
nanos = emptyWaitSet.awaitNanos(nanos);
                    } catch (InterruptedException e) {
e.printStackTrace();
                    }
                }
T t = queue.removeFirst();
fullWaitSet.signal();
return t;
            } finally {
lock.unlock();
            }
        }
// 阻塞获取
public T take() {
lock.lock();
try {
while (queue.isEmpty()) {
try {
emptyWaitSet.await();
                    } catch (InterruptedException e) {
e.printStackTrace();
                    }
                }
T t = queue.removeFirst();
fullWaitSet.signal();
return t;
            } finally {
lock.unlock();
            }
        }
// 阻塞添加
public void put(T task) {
lock.lock();
try {
while (queue.size() == capcity) {
try {
log.debug("等待加入任务队列 {} ...", task);
fullWaitSet.await();
                    } catch (InterruptedException e) {
e.printStackTrace();
                    }
                }
log.debug("加入任务队列 {}", task);
queue.addLast(task);
emptyWaitSet.signal();
            } finally {
lock.unlock();
            }
        }
// 带超时时间阻塞添加
public boolean offer(T task, long timeout, TimeUnit timeUnit) {
lock.lock();
try {
long nanos = timeUnit.toNanos(timeout);
while (queue.size() == capcity) {
try {
if (nanos <= 0) {
return false;
                        }
log.debug("等待加入任务队列 {} ...", task);
nanos = fullWaitSet.awaitNanos(nanos);
                    } catch (InterruptedException e) {
e.printStackTrace();
                    }
                }
log.debug("加入任务队列 {}", task);
queue.addLast(task);
emptyWaitSet.signal();
return true;
            } finally {
lock.unlock();
            }
        }
public int size() {
lock.lock();
try {
return queue.size();
            } finally {
lock.unlock();
            }
        }
    }
}